In the use of an electronic wrist instrument, it is usually necessary to have at least one push button which enables a user to select and engage desired functions of the wrist instrument. For example, where the electronic wrist instrument is a digital watch, the push button may be utilized by a user to illuminate the watch display by activating a light source, to select desired display functions, or to set information being displayed.
Typically, as shown in FIG. 1, the prior art push button assembly 10 for an electronic wrist instrument includes a push button member 12 having a stem 12a, where the push button member 12 is received by a bore 14 located in a portion of the wrist instrument's case 20. A retainer clip 16, such as an O-ring, is disposed about the stem 12a to retain the push button member 12 within the bore 14 and a spring 18 is disposed about the stem 12a to provide tension on the push button member 12. Furthermore, a dynamic seal 19 is disposed about the stem 12a to minimize or prevent moisture or other contaminants from entering the interior of the wrist instrument's case 20 where delicate electronic components can be adversely affected. As is well-known in the art, the push button assembly 10 functions by selectively operating a switch 24 connected to an integrated circuit (not shown) via an internal contact member 22.
Although the prior art push button assembly 10 of FIG. 1 is satisfactory from a performance standpoint, it is less than satisfactory in terms of construction and cost. From a construction perspective, the push button assembly of FIG. 1 is burdensome because there are required the steps of placing the spring 18 about the stem 12a, placing the seal 19 about the stem 12a, placing the push button member 12 into the bore 14 and placing the retainer clip 16 about the stem 12a. From a cost perspective, the push button assembly 10 of FIG. 1 is less than desirable because employing and assembling four separate components makes the push button assembly relatively high in cost.
An improved push button assembly is disclosed in U.S. Pat. No. 4,031,348 ('348) issued to Eberhardt on Jun. 21, 1977. As is the case for the push button assembly 10 of FIG. 1, the '348 push button assembly comprises a push button member and a retainer clip (in the form of a snap ring). However, unlike the push button assembly 10 of FIG. 1, the '348 push button assembly includes a resilient washer which dually functions as a spring and a seal. Since the '348 push button assembly employs one less component than the push button assembly 10 of FIG. 1, it offers both construction and cost advantages over the push button assembly 10 of FIG. 1.
Even though the '348 push button assembly offers advantages over the push button assembly 10 of FIG. 1, it would be desirable to provide a push button assembly which is a further improvement over the improved push button assembly of the '348 patent. Accordingly, it is the object of the present invention is to provide an improved push button assembly utilizing a minimum number of components and providing ease of assembly.